The electrode element is preferably intended for use as an anode in an electrolysis cell, such as is known from German Letters Patent DE-PS 36 40 020; because of a plurality of cathodes and comparatively few anodes, the electrolysis cell disclosed in this Letters Patent has an advantageous surface ratio of cathodes to anodes. Here, it is possible, for example, to separate the cathode chamber filled with waste water from the anodes by means of a diaphragm, so that the anode(s) are located in a closed-off anolyte chamber which protects the anode from the process liquid which might contain aggressive substances. The anolyte chambers are provided with their own electrolyte supply and removal devices for circulation. The anodes located in the anolyte chambers have a flat structure, and the anode surfaces are disposed parallel to the surfaces of the cathodes.
In this known device, the cover and corrosion of the diaphragm to be placed on the frame of the anodes as well as protection of the diaphragm against the metal precipitated on the adjacent cathodes presents problems, where it is possible, particularly when removing the cathode, that the adjacent diaphragm becomes damaged.
Furthermore, an electrode is known from U.S. Pat. No. 4,608,144 having a frame of electrically insulating plastic into which an electrode plate made on the basis of plastic is integrated. The lower part and the upper part of the insulated frame are each provided with a chamber-like liquid supply and liquid removal device which terminates in a plurality of individual conduits provided by the surface of the electrode structure. By the employment of a plurality of electrode plates disposed parallel to each other and separated by diaphragms, it is possible to construct a bipolar electrode with alternatingly inserted anode and cathode parts; such a bipolar electrode is suitable for chloralkali electrolysis. However, because of the lack of space between the cathode and the diaphragm, the precipitation of metal on this bipolar electrode is not possible.
An electrode arrangement in a metal recovery cell for cleaning industrial process solutions and waste water in a reservoir is known from European Patent Disclosure EP-OS 36 640, which for retaining plate-shaped electrodes has an open frame of parallel lateral strips as spacing elements and consists of electrically-insulating corrosion-resistant plastic; cathodes are disposed on both sides of the anode at a distance set by the frame, and no diaphragms or membranes are provided between the electrodes.
The cell is integrated into the reservoir and the input and output to the electrolysis chamber between the electrodes are kept free in order to obtain a circulation which generates gas bubbles between the reservoir chamber and the electrolysis chamber. On the one hand, the distance between the electrodes, must be large enough to provide space for precipitated metals but , on the other hand, not too great so that sufficient metal precipitation up to a remaining concentration of .ltoreq. 1 ppm of metal ions can be achieved.